OPNET Model of TCP with adaptive delay and loss response for broadband GEO satellite networks

Transmission control protocol (TCP) provides reliable transport services for Internet applications. Broadband geostationary earth orbit (GEO) satellite networks play an important role in providing Internet access and network connectivity. They are characterized by long propagation delays and high bit error rates, which negatively affect TCP performance. We proposed a modification of TCP named TCP with adaptive delay and loss response algorithm (TCP-ADaLR) that improves TCP performance in broadband GEO satellite networks. In this paper, we describe the TCP-ADaLR algorithm and its OPNET implementation. We evaluate and compare the performance of TCP-ADaLR, TCP SACK, and TCP NewReno, with and without delayed acknowledgment. To verify the algorithm implementation, we first consider simulation scenarios with an ideal lossless satellite link. We then consider simulation scenarios with congestion losses and show that TCP-ADaLR exhibits comparable performance to TCP SACK and TCP NewReno. In the presence of losses due to satellite link errors, TCP-ADaLR outperforms TCP SACK and TCP NewReno. In the presence of both congestion and error losses, TCP-ADaLR improves TCP goodput and throughput. In all simulation scenarios, TCP-ADaLR outperforms TCP SACK and TCP NewReno in terms of satellite link throughput and the userperceived latency of HTTP web and FTP file download applications. TCP-ADaLR is fair to competing connections, friendly to TCP NewReno, and maintains the end-to-end semantics of TCP.